1. Field of the Invention
The present invention relates to an electron-emitting device, an electron source having a multiplicity of the foregoing electron-emitting devices disposed therein, and an image-forming apparatus, such as a display apparatus or an exposure apparatus, formed by using the electron source.
2. Related Background Art
Hitherto, electron-emitting devices have been classified into thermionic emission devices and cold cathode electron-emitting devices. The cold cathode electron-emitting devices include, in the category thereof, devices of field emitting type (hereinafter called "FE" type), devices of metal/insulating layer/metal type (hereinafter called "MIM" type) and surface conduction electron-emitting devices.
As the FE type devices, there have been known a device disclosed in W. P. Dyke and W. W. Dolan, "Field Emission", Advance in Electron Physics, 8, 89 (1956), a device disclosed in C. A. Spindt, "Physical Properties of thin-film field emission cathodes with molybdenum cones", J. Appl. Phys., 47, 5248 (1976) and so forth.
As the MIM type devices, there have been known a device disclosed in C. A. Mead, "Operation of Tunnel-Emission Devices", J. Appl. Phys., 32, 646 (1961) and so forth.
As the surface conduction electron-emitting device, there have been known a device disclosed in M. I. Elinson, Radio Eng. Electron Phys., 10, 1290 (1965) and so forth.
The surface conduction electron-emitting device uses a phenomenon emitting electrons when an electric current is allowed to flow in parallel to the surface of a thin film having a small area and formed on an insulating substrate. As the surface conduction electron-emitting device, there have been reported the foregoing device disclosed by Elinson and using the thin SnO.sub.2 film, a device using a thin Au film [G. Duttmer: "Thin Solid Films", 9, 317 (1972)], a device using a thin In.sub.2 O.sub.3 /SnO.sub.2 film [M. Hartwell and C. G. Fonstad: "IEEE Trans. ED Conf.", 519 (1975)], a device using a thin carbon film ["Vacuum" Vol. 26, 1st issue, p.p. 22, by Hisashi Araki et al. (1983)] and so forth.
The surface conduction electron-emitting device uses the phenomenon emitting electrons when an electric current is allowed to flow in parallel to the surface of a conductive film formed on an insulating substrate.
A typical structure of the surface conduction electron-emitting device is shown in FIGS. 28A and 28B. Note that structure shown in FIGS. 28A and 28B has been disclosed by the applicant of the present invention. Referring to FIGS. 28A and 28B, reference numeral 2001 represents a substrate, 2002 represents an electron-emitting portion, 2003 represents a conductive film including the electron-emitting portion 2002, and 2004 and 2005 represent electrodes of the device.
In the surface conduction electron-emitting device, the electron-emitting portion 2002 is usually previously formed in the conductive film 2003 made of conductive fine particles by an electric current flowing treatment called "forming". The forming process is usually performed by applying voltage to the two ends of the conductive film 2003 to locally rupture, deform or denature the conductive film 2003 so as to change the structure so that the electron-emitting portion 2002 in an electrically strong resistance state is formed. Note that a fissure is formed in a portion of the conductive film 2003 of the electron-emitting portion 2002, thus causing electrons to be emitted from the portion in the vicinity of the fissure.
The foregoing surface conduction electron-emitting device, having a simple structure as described above, has an advantage that a multiplicity of devices can be disposed over a large area. To use the foregoing characteristic, a variety of applied forms have been developed, for example, an application to an image-forming apparatus, such as a charged beam source or a display apparatus.
As a conventional structure having a multiplicity of surface conduction electron-emitting devices disposed therein, there is exemplified by an electron source having a structure such that surface conduction electron-emitting devices are disposed in parallel, the two ends of each of the surface conduction electron-emitting devices are connected by wires (also called "common wires") to form a row, and a multiplicity of the rows are disposed (also called a "ladder-type configuration")(refer to, for example, Japanese Patent Laid-Open Application No. 64-31332, Japanese Patent Laid-Open Application No. 1-283749 and Japanese Patent Laid-Open Application No. 2-257552).
As a display apparatus which can be formed into a flat display apparatus similar to a display apparatus using liquid crystal and with which a spontaneous light emitting type display apparatus that does not require a backlight can be formed, a display apparatus has been suggested which is formed by combining an electron source, comprising a multiplicity of surface conduction electron-emitting devices, with fluorescent members which emit visible rays when irradiated with electron beams emitted by the multiplicity of the electron sources (refer to U.S. Pat. No. 5,066,883).
Hitherto, devices caused to emit fluorescent light when irradiated with electrons emitted by the electron source formed by the multiplicity of the surface conduction electron-emitting devices have been selected in response to appropriate drive signals supplied to wires (called "row-directional wires"), in parallel, connecting the multiplicity of the surface conduction electron-emitting devices and to control electrodes (called "grids") disposed in a space between the electron-emitting devices and the fluorescent members, the grids being disposed perpendicular to the row-directional wires (refer to, for example, Japanese Patent Laid-Open Application No. 1-283749 laid open by the applicant of the present invention).
When the electron-emitting device for use in the electron source or the image-forming apparatus is operated for a long time, stable and controlled electron-emitting characteristics and improvement in the efficiency in emitting electrons have been required.
The foregoing efficiency is, in the case of the foregoing surface conduction electron-emitting device, the ratio of an electric current (hereinafter called a "device current If") flowing when voltage is applied to a pair of opposite device electrodes and an electric current (hereinafter called an "emitted current Ie") emitted into a vacuum. That is, the improvement in the electron-emitting efficiency is to reduce the device current If as possible and to enlarge the emitted current Ie as possible. If stable and controlled electron-emitting characteristics are obtained and the efficiency in emitting electrons is improved, an image-forming apparatus comprising, for example, fluorescent members as image-forming elements thereof can be formed into a bright and high-grade image-forming apparatus requiring a small electric current, for example, a flat TV monitor can be realized. Furthermore, since only a small electric current is required, the overall cost of the drive circuit and the like forming the image-forming apparatus can be reduced.